Photo-assisted rechargeable supercapacitors based on nickel-cobalt-deposited tungsten-doped titania photoelectrodes: A novel self-powered supercapacitor

Abstract

Photo-rechargeable supercapacitors, which are encouraging energy storage devices, have attracted much attention given their potential applications in smart electronics. They offer an appealing method for the application of sustainable solar energy. In this work, nickel-cobalt (NiCo) are deposited on a tungsten-doped TiO2 nanotube (WTs) substrate by electrodeposition using various deposition cycles in order to investigate the effects of electrodeposition cycle change on microstructure and electrochemical properties of prepared samples. According to the obtained results, sample NiCo-10 (is deposited for 10 cycles) has the optimum specific capacitance of 252.4 mF/cm2 at the 0.71 mA/cm2 current density in 3.0 M aqueous KOH. The optical properties of the prepared electrodes are studied by using the supercapacitor under light illumination. The areal capacitance of the fabricated supercapacitor is enhanced by ∼68.3% at a 20 mV/s scan rate under illumination by light. The photo-charging and galvanostatic discharging of the device have also been investigated. The maximum photo-charged areal capacitance value obtained is 75.2 mF/cm2 at a 0.04 mA/cm2. However, the power density and areal energy at this current density are 7.54 mW/cm2 and 33.93 mW h/cm2, respectively. Thus, the good electrochemical property makes NiCo@WTs promising photoelectrodes in the area of energy storage for photo-assisted rechargeable supercapacitors.